Line driver amplifiers remain a bottleneck in modern analog circuit design. Their integration with other analog circuit components is problematic. One reason for this is that the need to employ relatively large magnitude supply voltages prevents realizing the advantages that would result from using finer and much faster integrated circuit technology. Other reasons include large power consumption, and sensitivity to noise coming from power supplies and the integrated circuit substrate. Indeed, a properly designed line driver amplifier should have well-controlled quiescent currents in its output transistors along with the ability to provide much larger magnitude currents during the transient state. Additionally, in many applications the line driver amplifier distortion characteristics at high frequencies are very important.
In prior known line driver amplifier arrangements the transconductance of the amplifier output transistor changes with current. Consequently, the amplifier bandwidth is dependent on the output transistor current. This results in dynamic distortion in the amplifier output causing non-linearity in the frequency domain.